Physical signals are increasing recognized as playing an important role in modulating cell behavior. The goal of this proposal is characterize the cellular response to force-mediated signaling in the intestine of zebrafish meltdown mutants. We have shown that an activating mutation in smooth muscle myosin heavy chain gene myh11 disrupts intestinal architecture in meltdown mutants. Physical signals arising from the mutant myosin activate a conserved redox signaling pathway in the invasive epithelium that has been linked to vascular remodeling and cancer cell invasion in humans and animal models. The goal of this proposal is to further characterized the response of the meltdown intestinal epithelium to physical force and understand how it activates redox signaling that drives formation of invadopodia and cell invasion. The goal of the first aim is to identify the source of epithelial reactive oxygen species (ROS) in meltdown and the mechanotransductive signaling mechanism that activates ROS production downstream of unregulated myosin. The goal of the second aim is to define how changes in the expression of cell migration and lipid synthesis genes identified through transcriptional profiling experiments influence cell invasion in meltdown. The goals of the third aim are to molecularly characterize novel dominant mutations that induce cell invasion in meltdown heterozygotes, and to continue screening for additional dominant enhancing mutations using chemical mutagenesis. Collectively, the proposed experiments will define novel factors and cellular mechanisms that maintain intestinal architecture in vivo. This work will thus enhance our understanding of mechanisms regulating homeostatic and injury induced tissue regeneration in the intestine, as well how intestinal cancers undergo invasive transformation.